Glow stick

Made from a stick and glowing goop (an item dropped by the glow squid) it acts like a torch that can be placed out of and in water. However it gives off less light than a torch. You can also use dyes to change the color of the glow stick which changes the color of the light it gives off. Good for under water lighting and with the colors can be a great way to create a atmospheric effect that will go great with any build.